Hussam Hertani wrote:

> 1-When using the function attribute:
> "__attribute__ ((long_call, section (".data")))" does this store the
> function purely in RAM or does it store it in FLASH and then load it
> into ram on runtime..i.e. if the device is reset will ths function
> disappear?

The funtion-code is also in Flash since it has to be compied into RAM
after Power-On or Reset. It gets executed from RAM. The code may still
be in RAM on Reset depends on how the controller internly initializes
it's RAM.

> 2-If i use .fastrun or .data in the above function attribute declaration
> does it make any difference?

An extra section ".fastrun" (or whatever name you choose) provides
better control i.e. to determine the size of the fastrun-functions and
for alignment in the linker-script. The basic handling is the same. Make
sure to adapt the linker-script if you a "choosen" section and not data.

> 3-Does the linker store the .data and .bss sections in ram only or does
> it store them in flash and then load them into ram at runtime? and what
> is the difference between this definition
>
> .data :
> {
>
>  _data = .;
> *(.data)
> _edata = .;
> } >ram AT >flash
>  and this one in the linker script ? (">ram" vs ">ram AT > flash")
> .data :
> {
>
>  _data = .;
> *(.data)
> _edata = .;
> } >ram

.data is used for initialization so a copy of these values is needed in
persistant memory. So data "consumes" Flash and RAM. Variables in bss
are known to init with 0 so no flash ist needed for
initialization-values.

> 4-I realize that in the LPC2XXX devices that the Interrupt vector table
> can be remapped into RAM by setting the Memmap bits appropriately...How
> would i code the ISR's in RAM as well

Use a section-attribute and place this section in RAM. Some of my
examples demonstrate this.

> 5-In the linker scripts (almost all the ones i saw) what does this do?
>
> .stack ALIGN(256) :
>
>   {
>
>     . += STACK_SIZE;
>
>     PROVIDE (_stack = .);
>
>   } > RAM

Reserves space for the stack in RAM for a setup where the stack located
is between "data" and "heap".

> 6- Finally,in the lpc2129_ramfunction_20050510.zip there are two linker
> scripts; RAM-based one for debugging and the rom_based one for
> execution...why does the RAM-based one define ENTRY at _start and the
> ROM-based one define ENTRY at _boot?

Hmm, don't remember why. Have to look at this code later.

Martin